In recent years, study on organic compounds of germanium (a homologue of carbon) has actively been conducted, and many study results have been presented or published. Thus, attention is being paid to organogermanium compounds in various fields, particularly medical and pharmaceutical fields.
For example, it is reported that carboxyethylgermanium sesquioxide (Japanese Patent Publication No. 2498/1971) which is an organogermanium compound formed by bonding of a propionic acid derivative of germanium and oxygen atom at a 2:3 ratio shows a hypotensive action to spontaneous hypertensive rats, an amyloidosis-alleviating action, a macrophage-augmenting action, an interferon-inducing action, an antitumor action, etc. The above sesquioxide is in trial use clinically.
The above carboxyethylgermanium sesquioxide is a compound represented by a chemical formula (Ge--CH.sub.2 --CH.sub.2 --COOH).sub.2 O.sub.3 The so far developed organogermanium compounds are not restricted to the above compound alone and include cylic compounds represented by the following general formula. ##STR3## On the above cyclic compounds, patent application was made by Japanese Patent Application Kokai (Laid-Open) No. 267591/1986.
The above cyclic compounds contain a Ge atom as a ring-forming element. Since germanium atom is tetravalent, if there is developed an organogermanium compound of different chemical structure which contains a germanium atom in the form of, for example, a spiro-atom, it is highly possible that such an organogermanium compound find novel utility.
However, there has hitherto existed no organogermanium compound which contains a germanium atom in the form of a spiro-atom. Therefore, it has been desired to develop such an organogermanium compound and its useful application.